I asked to Robin Nigel Fox, friend of Thomas Neubau, another expert that live in Italy and here is the answer:

Yes, you have identified it correctly. In most colonies of the Argynnis paphia, there are some females that are not of the ordinary orangey-brown colour, but that have this lovely purple-blue colouration. The light on your example brings out the colour fantastically.

There are no other paphia forms , as far as I know. I get my information from the Collins Butterfly Guide by Tom Tolman and Richard lewington.